This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Background: Oxidative stress may contribute to ventricular and vascular remodeling, and disease progression in patients with heart failure. Xanthine oxidase (XO) is a potential source of oxidative stress in heart failure, and may be an important target for therapy. Allopurinol is an XO inhibitor, which reduces serum uric acid levels, and may be useful in the treatment of patients with systolic heart failure (HF). Hypothesis: In patients with symptomatic heart failure due to left ventricular systolic dysfunction and elevated serum uric acid levels, treatment with allopurinol for 24 weeks will improve clinical outcomes compared to treatment with placebo.